Electrodeposition of metals



- art.

Patented July 28, 1942 2,291,590 I C E 2,291,590 amo'monnrosrrron orMETALS Rudolf Lind, Euclid, William J. Harshaw, Shaker Heights, andKenneth E. Long, South Euclid, Ohio, asslgnors to The Harshaw ChemicalCompany, Elyria, Ohio, a corporation of Ohio No Drawing. ApplicationMarch 11, 1940,

Serial No. 323,380

17 Claims.

This invention relates as indicated to electrodeposition of metals andmore specifically, to a process of and materials for use in the processof electrodepositing nickel characterized in that the resultant nickelplate, as deposited, is both bright and ductile. More particularly, thepres ent invention has to do with new addition agents for producing theabove-named desirable characteristics in the nickel plate and which maybe used with acid nickel baths of usual composition operating underusual conditions.

In order to properly evaluate the present invention, it is necessary todefine brightness and ductility or brittleness, terms used in the oldart, but used loosely to describe all degrees of brightness orbrittleness.

BRIGBTNESS It is obvious that an extremely thin deposit of nickel over ahighly buffed surface will appear bright. Bright plates of this typehave been made for years and are well recognized in the article isexposed to the atmosphere or to wear, the plate soon disappears or wearsoff. A plate thin enough so that it will retain substantially the fullbrightness of the polished base metal is impractical for use even as abase for the electrodeposition thereover of a protective coating ofother metals such as chromium. If a heavier deposit is plated out, thebrightness of the highly buffed surface diminishes and a gray or whitedull deposit is obtained.

A nickel plate which is thick enough to be practical for use and whichis brought without bufling is not only desirable per se, but it isparticularly advantageous where it is destined for use as the base foran electrolytically deposited chromium plate, since, if the nickel platedoes not require to be polished and bufied, a relatively thin plategives the same protection as the necessarily heavier gray plate, some ofwhich must be taken off in the polishing to secure the desiredbrightness. Furthermore, a very considerable saving in time and in coston the production of plated articles becomes possible, whether withnickel plate per se or with additional chromium finish.

Various so-called addition agents have been proposed from time to timefor inclusion in nickel plating baths in order to control or afiect thecharacter of the electrolytically deposited metal. One principalobjective in such modification of the plating bath has been to increasethe brightness or luster of the deposited metal.

Many of these previous nickel plating addition agents have allowed amuch heavier deposit of nickel to be built up before the brightness ofthe base metal was materially diminished. When polished articles areplated in such baths, the

Their limitations are that if the plated deposit is not truly bright butmerely, at best, has the same character as the base metal. Thebrightness produced by such addition agents may, therefore, becharacterized as-brightness diminishing with increased thickness ofplate on a polished surface.

Others of these previous nickel plating addition agents have produced aplate which would maintain the brightness of the polished base surface,even though the plate was built up to a substantial thickness. Theywould not build up any substantial brightness on an unpolished surfaceand, at best, would only very slowly build up brightness on anunpolished surface when plates of extreme thickness were made. Thebrightness produced by such addition agents may, therefore, becharacterized as brightness maintaining itself with increased thicknessof plate on a polished surface.

The addition agents of produce a plate that not only maintains thebrightness of the most highly polished base metal, irrespective of thethickness of the plate within practical limits, but also increases inbrightness with increase in thickness of the plate on an unpolishedsurface. The brightness produced by such addition agents may, therefore,be characterized as brightness increasing with thickness of plate on'anunpolished surface.

DUCTILITY The question of ductility is one of vital concern to theplater. harder and, therefore, more brittle than ordinary dull nickel.When enough of many of. the previously employed addition agents wasadded to a bath to produce a bright plate, the plate was often toobrittle for commercial use and yet if less addition agent was used, theplate would not be fully bright. A test for ductility may be made byplating on a non-adherent surface and stripping off the foil and bendingit double on itself. A plate .001" thick which will pass this testwithout breaking is considered to have good ductility. A plate .0005"thick which will just pass this test is considered to have passableductility. A plate .0002" thick which will not pass this test withoutbreaking is considered to have poor ductility.

The addition agents of the present invention not only produce plateswith the highest order of brightness, but also with a high order ofductility as defined by the above scale. This is desirable and essentialto the practical use of bright nickel plating.

The principal object of the present invention, therefore, broadlystated, is to provide an improved process of and materials for use inthe process of electrodepositing nickel which will not only render thenickel plate desirably bright but the present invention In general, allbright plates are,.

which will also preserve or render the plate desirably ductile.

Other objects of our invention will appear as the description proceeds,

To the accomplishment of the foregoing and related ends, said invention,then, consists of the means hereinafter more particularly pointed out inthe claims, the following description setting forth in detail certainapproved modes of operation of our process and combination ofingredients embodying our invention, such disclosure constituting,however, but certain of various forms in which the principles of ourinvention may be used.

Broadly stated, our invention. comprises the discovery that by the usein acid nickel electrolytes of a plurality of addition agentsrespectively selected from certain different classes of compounds, weare able to produce deposits which are superior to those obtainable bythe use of addition agents from either one of such classes alone. Wefind that the addition agents from one of said classes, althoughcharacterized by an embrittling tendency, are productive of extremebrightness when used in combination with addition agents from the otherclass and that addition agents from said other class not only cooperatein the production of brightness but also exert a ductilizing effect inthe combination. The use of one addition agent from each class ispreferable but a plurality from each class can be used successfully. Ourcooperating addition agents are suitable for use in a wide variety ofnickel electroplating solutions. we have found them to be very effectivein aqueous acid nickel sulfate solutions and aqueous acid nickelchloride solutions. Among the nickel sulfate solutions in which they areeffective are aqueous acid solutions of nickel sulfate, nickel sulfateand nickel chloride, nickel sulfate and sodium chloride, nickel sulfateand hydrochloric acid, nickel sulfate and ammonium chloride, nickelsulfate and alkali metal chlorides other than sodium chloride, thechlorides serving to produce good anode corrosion. Our addition agentsare effective in nickel chloride solutions with and without nickelsulfate. In each of said solutions it is desirable, although notnecessary, to employ boric acid or another suitable buffering agent. Weprefer to employ a bath containing nickel sulfate together with asuitable chloride, preferably nickel chloride and a suitable buffer,preferably boric acid. We prefer to employ one or more addition agentsfrom one of said classes in quantity to produce the desired brightnessand one or more from the other class in quantity to overcome to asubstantial extent the resulting embrittling tendency.

Representative of separate classes of mpounds which, when used incombination as above stated, produce improved results, are those classesof compounds which may be identified as (1) aromatic compoundscontaining the group classes of addition agents are distinct, they willbe discussed separately.

Aromatic nitrogen compounds Our invention contemplates, as indicated,the use of aromatic compounds of adequate solubility containing thegroup group, etc. The bonds shown to each aryl group are ortho to eachother and the links connecting the Ar and Ar groups with N and :1:indicate single or double bonds. We do not know with certainty in allcases what type of bond exists but we have made use of materials havingthe acridine, azine, thiazine and oxazine nuclei. Reference is made toSchultz, infra, for accepted the- I cry of structure of these nuclei,the expression z Ar Ar' N being intended to indicate them generically.Ar and Ar may be identical or different. Ar and Ar indicate aromaticcyclic structures such as, for example, benzene or naphthalene nucleiwhich carry substituent groups. We prefer to employ compounds carryingone or more amino groups connected to ring carbon. Alkyl amino or arylamino substituents such as N(Me)z. NHMe, --N(Ph)2 and the like also aredesirable and may be regarded as amino groups. Compounds containingalkyl, such as methyl, ethyl, etc., halogen, sulfonate, hydroxy andnitro groups may also be used. The substituent groups such asaminogroups, including alkyl amino groups, appear to be desirable assuch while groups such as the sulfonate and halogen groups, unlessneeded to improve the solubility, apparently are undesirable orindifferent.

The salts of such of these compounds as are basic, e. g. the chlorides,hydroohlorides, acetates and sulfates are to be preferred to such basiccompounds themselves because of their greater solubility. It isessential that these compounds, a single one or a mixture of two or'morethereof, be present in the solution to an extent to exert theirbrightening eflect. preferably at least two milligrams per liter.

Some specific examples of compounds suitable for our purpose are asfollows, being identified where possible by reference toFarbstofitabellen by Gustav Schultz, 7th edition, volume I (1931).

TABLE I l. Tetramethyl diamino acridine hydrochloride.

Schultz No. 902. An acridine dye, Rhodamine Orange, or Acridine Orangehaving the nucleus and carrying for methyl and two amino substituents.)

2. Dimethyl diamino acridine hydrochloride. 8. Diamino acridinehydrochloride.

Ar and Ar representing benzene nuclei.) 4. Diamino diphenazine.

Ar and Ar indicating benzene nuclei.) Safranine Y. Schultz 'No. 967. (Amixture of two dyes of the azine type, i. e. having the nucleus N Ar Ar)N ms-Phenyl diamlno diphenylazonium chloride.

(A compound of the formula ride. Oxazine nucleus.) 10. Diaminophenoxazine.

(H:N.Al' AI'NH:

Ar and Ar indicating benzene nuclei.)

-Lauths Violet, Diamino diphenazthionium chloride. Schultz No. 1036.(Thiazine nucleus.)

Methylene Blue. Schultz No. 1038. (Tetramethyl diamino diphenazthioniumchloride.)

Methylene Green B. D. Schultz No. 1040.

(Tetramethyl diamino nitro diphenazthionium chloride. Thiazine nucleus.)Toluidine Blue. Schultz No. 1041. (Dimethylamino phenoaminotolazthionium chloride. Thiazine nucleus.)

Thionine Blue SO. Schultz No. 1042. (Trimethyl ethyl diaminodiphenazthionium chloride. Thiazine nucleus.)

New Methylene Blue. Schultz No. 1043. (Diethyldiamino ditolazthioniumchloride. Thiazine nucleus.)

Thiocarmine R. Schultz No. 1044. (Sodium salt of sulfonic acid ofsymmetric diethyl dibenzyl diamino diphenazthionium sulfonate; internalsuli'onate.)

Brilliant Alizarine Blue G. A. Schultz No.

1048. (Dimethylamino dihydroxynaphthophenazthionium sulfonate and/orbenzyl ethylamino dihydroxy naphtho phenazthionium sulfonate.)

While the quantity of these substances employed is not sharply critical,they are used in small amounts, that is, amounts of the order of 2 to100 milligrams per liter of the bath, the upper limit being determinedby their embrittling effect and in some cases, their solubility.

Most of the specific examples given in Table wherein Ar and Ar representbenzene nuclei, carrying at least one amino group on each benzene ringbut not more than three amino groups on either benzene ring andtheirsalts such as chloride, hydrochloride, acetate and sulfate are ofoutstanding value from the standpoint of control of the operation of thebath and are somewhat superior in respect to brightening effect to themore complex compounds. g The second class of materials, representativeparticular ones of which are employed in combination with one or moresubstances of the first class of compounds above identified, may be andfor the purposes of this specification are designated as aromaticsultan-compounds. These materials are capable of cooperating with' thematerials of the first class to produce nickel deposits having a highorder of brightness accompanied by commercial ductility.

Particular examples which we have found to give excellent results are asfollows:

TABLE II Alpha-naphthalene mono-sulfonate Beta-naphthalenemono-sulfonate Naphthalene disulfonates Naphthalene trisulfonatesSulfonated naphthalene o-Benzoic sulfimide (saccharin,.pre1erably assodium salt) 7. Benzene sulfonamide 8. Benzene sulfohydroxamic acid 9.p-Toluene sulfonamide 10. o-Toluene sulfonamide "The above namedaddition agents of this second class, suitably in the form of the sodiumor the nickel salt, may be used in various quantities upwards from 0.2g./l., however, 5 g./l., or less is usually suificient concentration forbest results. Larger quantities, within the limits of solubility, do noharm.

Specific Example 5 of Table II above is such as may be produced byreacting 2 parts of 20% oleum on one part of naphthalene at C. for twohours, neutralizing the resulting mixture with nickel carbonate.filtering and diluting to 26 B. Where quantities of sulfonatednaphthalene" are referred to hereinafter, it is to be understood thatthe quantity specified represents roughly thenickel-naphthalene-mixed-sulfonate content of the mixture. Five cc. ofthe nickel neutralized reaction mixture is taken as equivalent .to onegram of nickel-naphthalene-mixed sulfonates. Other mixtures of compoundsof the second class of materials also are satisfactory.

A conventional aqueous acid nickel bath in which the combined use of thetwo classe of addition agents will be found to give improved results, asabove indicated, consists of NiSO4.6HaO' 120-450 grams per literNiC12.6H2O 15-75 grams per liter HaBOa 15 grams per liter to saturationSodium lauryl sulfate -1.0 grams per liter Current density Up to 60amperes per sq .ft. pH... ...1.5-5.5 Temperature Room to 170 F.

referred to. the material Where this compound is M. E. Dry is sold underthe trade name of Duponol to be understood. It is sold as the techjncalcompound. Other equivalent surface tension reducing agents may be usedinstead of Duponol. Preparations known as Tergitol 7 and- Tergitol 08,sold by Carbide & Carbon Chemicals Co. and said to be sodium secondaryalcohol sulfates. may be used instead of Duponol. The quantitiesrequired are of the same order.

Some heptahydrate is usually present. Where nickel sulfate is usedherein in specific examples, this mixture of hydrates is to beunderstood.

In the above table giving the composition of a conventional bath, sodiumlauryl sulfate is added for the purpose of reducing the surface tensionin order to prevent pitting of the plate. The sulfates of normal primaryaliphatic alcohols, having from 8 to 18 carbon atoms, are a class ofcompounds preferred for use for this purpose.

The following specific examples will serve to illustrate the invention:

EXAMPLEI Nickel sulfate grams 240 Nickel chloride do 37.5 Borac acid do37.5 Mixture of ms-phenylditolazonium chloride andms-o-tolylditolazonium chloride (Safranine Y) gram 0.01 o-Benzoicsulfimide (saccharin, sodium salt) grams 2.0 Sodium lauryl sulfate do0.25

Water to make liter 1 pH 4. 0 Temperature C 50 Current density amp./sq.ft 40 EXAMPLE II Nickel sulfate; grams 240 Nickel chloride do.. 37.Boric acid do 37.5 Dimethylaminophenonaphthazoxonium chloride (BasicNavy Blue D cone.)

am" 0.030 Sulfonated naphthalene (nickel salt) grams 4.0

Water to make liter 1 pH 4.0 Temperature C 50 Current density amp./sq.ft. 40

' EXAMPLE III Nickel sulfate grams 240 Nickel chloride do 37.5 Boricacid do 37.5 Tetramethyldiaminodiphenazthionium chloride (MethyleneBlue, extra, conc. do 0.025 Sulfonated naphthalene ,(nickel salt) do 5.0Sodium lauryl sulfate do 0.25 Water to make liter 1 pH 3.3 TemperatureC-.. 60 Current density -amp./sq. ft 50 EXAMPLE IV Nickel sulfate grams240 Nickel chloride do 37.5 Boric acid do 37.5 5Tetramethyldiaminonitrodiphenazthionium chloride (Methylene 'Green BD)do 0.025

"Sulfonated naphthalene (nickel salt do 4.0

Water to make liter 1 pH 4.0 Temperature L C 50 Current density amp./sq,ft 40 5 ExAMrLaV Nickel sulfate grams 240 Nickel chloride do 37.5 Boricacid do 37.5 Rhodamine Orange (or Acridine Orange,

20 Schultz #902) milligrams Sulfonated naphthalene" cc 5 Water to makeliter 1 pH 3.5 Current density amp./sq. ft 40 25 EXAMPLE VI Nickelsulfate grams 240 Nickel chloride do 37.5 Boric acid do 37.5

Nigrosine (Schultz #986) milligrams 100 Sulfonated naphthalene cc 20Sodium lauryl sulfate gram 0.25 Water to make liter 1 pH 3.0

Temperature C 60 Current density amp./sq. ft 50 EXAMPLE VII Nickelsulfate grams 240 40 Nickel chloride do 37,5 Boric acid -4 do 37.5Induline R (Schultz #984) milligrams 25 Sulfonated naphthalene cc 5Sodium lauryl sulfate gram 0.25

Water to make liter 1 pH 3.5 Temperature C 45 Current density amp./sq.ft 40 EXAMPLE VIII Nickel sulfate grams 240 Nickel chloride do 37.5Boric acid do 37.5 Lauths Violet (Schultz #1036) milligrams 25Sulfonated naphthalene" cc 3 saccharine (soluble, soda salt) gram 0.5Sodium lauryl sulfate do .25 Water to make liter 1 Temperature C 60Current density amp./sq. ft 40 This application is acontinuation-in-part of our co-pending application, Serial No. 217,774,filed July 6, 1938, now Patent No. 2,238,861. This application is also acontinuation-in-part of our co-pending applications, Serial Nos. 309,232and 309,233 filed December 14, 1939, now Patents No, 2,198,267 and No.2,198,268, respectively, which were in turn continuations-in-partrespectively of our applications, Serial Nos. 200,120 and 200,121, filedApril 5, 1938.

Having thus described our invention, what we claim is:

1. An electroplating bath comprising an aqueous, acid solution of anickel electrolyte of the where a: is selected from the group consistingof N, 0,8 and O, and which are soluble in the bath to the extent of atleast one milligram per liter and mixtures of such compounds, and theother of said addition agents being selected from the class consistingof naphthalene sulfonates, the

single ring aryl sulfonamides and single ring aryl sulfimides andmixtures thereof present in solution in the bath to the extent of atleast 0.2 gram per liter. Y

2. An electroplating bath comprising an aqueous, acid solution of anickel electrolyte of the class consisting of nickel sulfate and nickelchloride, said solution having the capability of producing bright andductile deposits of nickel, such capability having been imparted theretoby the inclusion therein of cooperating addition agents, one of saidaddition agents being maintained in solution in the bath in quantityfrom 2 to 100 milligrams per liter and being selected from the group ofcompounds containing the grouping I where a: is selected from the groupconsisting of N, C, S and 0, having requisite solubility to permit suchconcentration and mixtures of such compounds, and the other of saidaddition agents being selected from the group consisting of naphthalenesulfonates, the single ring aryl sulfonamides and single ring arylsulfimides and mixtures thereof present in solution in the bath to theextent of at least 0.2 gram per liter.

3. An electroplating bath as defined in claim 2 further characterized inthat said first mentioned addition agent comprises a. compound having atleast one amino group connected to ring carbon.

4. An electroplating bath as defined in claim 2 further characterized inthat said first men?" tioned addition agent is an azine compoundhavingba't least one amino group connected to ring car 11.

5. An electroplating bath as defined in claim 2 further characterized inthat said first mentioned addition agent is diamino diphenazine.

6. An electrodeposition bath as defined in claim 2 further characterizedin that said first mentioned addition agent is diamino acridinehydrochloride.

. 7. An electrodeposition bath as defined in claim 2 furthercharacterized in that said first mentioned addition agent is IauthsViolet.

8. An electroplating bath comprising an aqueous, acid solutioncontaining nickel sulfate and nickel chloride, said solution having thecapability of producing bright and ductile deposits of nickel, suchcapability having been imparted thereto by the inclusion therein ofcooperating addition agents,'one of said addition agents beingmaintained in solution in the bath in quantity from 2 to 100 milligramsper liter and being selected from the group of compounds containing thegrouping 1 Ar Ar' where :c is selected from the group consisting of N,C, S and 0, having requisite solubility to permit such concentration andmixtures of such compounds, and the other of said addition agents beingselected from the group consisting of naphthalene sulfonates, the singlering aryl sulfonamides and single ring aryl sulfimides and mixturesthereof present in solution in the bath to the extent of at least 0.2gram per liter.

9. An electroplating bath as defined in claim 8 further characterized inthat said first mentioned additionagent comprises a compound having atleast one amino group connected to ring carbon.

10. An electroplating bath as defined in claim 8 further characterizedin that said first mentioned addition agent. is diamino diphenazine.

11. An electrodeposition bath as defined in claim 8 furthercharacterized in that said first mentioned addition agent is diaminoacridine hydrochloride.

12. An electrodeposition bath as defined in claim 8 furthercharacterized in that said first mentioned addition agent is LauthsViolet.

13. The electroplating bath as defined in claim 1 wherein the secondmentioned addition agent is an ortho benzoic sulfimide (saccharine,soluble saccharine).

14. The electroplating bath as defined in claim 8 wherein the secondmentioned addition agent is an ortho benzoic sulfimide (saccharine,soluble saccharine).

'15. An electroplating bath as defined in claim 2 further characterizedin that said first men-,- tioned addition agent is diamino diphenazineand said second mentioned addition agent is an ortho .16. Anelectroplating bath as defined in claim 2 further characterized in thatsaid first mentioned addition agent is diamino acridine hydrochlorideand said second mentioned addition agent is an ortho benzoic sulfimide.

